It is hypothesized that the mean reduction baseline in net urinary sodium excretion during the first 72 hours of treatment with oral L-748,731 (50 mg q.d.) will be similar to the mean reduction during the first 72 hours of treatment with oral indomethacin (50 mg t.i.d.) in subjects 60 to 80 years of age consuming a 200 mEq sodium diet (i.e., the difference in mean reduction will be within +/- 90 mEq). Administration of oral L-748,731 mg daily for 2 weeks to subjects 60 to 80 years of age will be sufficiently safe and well tolerated, based on assessment of clinical and laboratory adverse experiences, to permit continued clinical investigation of this drug. The specific aims are: 1) To compare the effects of treatment with oral L-748,731 50 mg q.d., indomethacin 50 mg t.i.d., or placebo on urinary sodium excretion over the initial 72 hours of treatment in subjects 60 to 80 years of age consuming a 200 mEq sodium diet; 2) To compare the safety and tolerability of 2 weeks of treatment with oral L-748,731, 50 mg q.d., oral indomethacin, 50 mg t.i.d., or placebo in subjects 60 to 80 years of age consuming a 200 mEq sodium diet; 3) To compare the effects of treatment with oral L-748,731, indomethacin, or placebo on change in body weight as an index of sodium retention; 4) To compare the effects of treatment with oral L-748,731 indomethacin, or placebo on net urinary sodium excretion over the first week and over the total of 2 weeks of treatment; 5) To compare the effects of 2 weeks of treatment with oral L-748,731, indomethacin, or placebo on iohexol and creatinine clearances; 6) To compare the effects of treatment with oral L-748,731, indomethacin, or placebo over a period of two weeks on blood pressure; 7) To compare the effects of 2 weeks of treatment with oral L-748,731, indometacin, or placebo on other parameters of renal function/prostaglandin metabolism, including urinary potassium excretion, urinary eicosanoids, serum TXB2, and urinary N-acetyl-beta-glucosaminidase (NAG).